Ship provided with a distortion sensor and distortion sensor arrangement for measuring the distortion of a ship

ABSTRACT

An improved ship which incorporates a distortion sensor arrangement. Measurement data supplied by the distortion sensor arrangement is preferably used to correct measurement data supplied by and/or control signals for an on-board directional apparatus. The distortion sensor arrangement preferably includes a hull-mounted laser beam/light sensor combination, and such that the light sensor continuously measures a deflection of the laser beam in response to a distortion of the ship.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a ship and, more particularly, to a naval ship.

2. Discussion of the Background

In general, ships have a limited rigidity. Modern naval ships inparticular are of a thin-walled construction with a view to optimalweight reduction. A drawback of the limited rigidity is that the ship isliable to distortion caused by, for instance, sea state, differences intemperature or payload. This drawback particularly manifests itself ifthe ship is provided with a measuring instrument for performing angularposition measurements of objects in relation to the ship. For anaccurate angular position measurement, the angular position of themeasuring instrument itself shall be accurately known. This angularposition is usually determined in an alignment procedure. In the processof time, however, this angular position is apt to change as a result ofthe ship's distortions.

SUMMARY OF THE INVENTION

The ship according to the invention has for its object to obviate thisdrawback and is thereto provided with a distortion sensor for at leastsubstantially continuously measuring distortions of the ship.

An additional advantage is that the rigidity of the ship needs no longerbe such that the measuring instrument is susceptible, in relation to themeasuring error, to an angular displacement that is still acceptable.This means that the weight and, consequently, the cost of the ship canbe reduced.

The distortion measurements can now, at least substantially continuouslyand during service conditions, be presented on a display or be used forany other purpose.

In an advantageous embodiment the distortion measurements are used toascertain the ship's torsional and bending distortions as these largelyaffect the position of onboard equipment units. Particularly torsionaldistortions about the longitudinal axis and bending distortions aboutthe transverse axis are relevant in this respect.

An advantageous embodiment in which the ship is provided with at leastone target sensor and a processing unit for processing the measurementdata supplied by the target sensor is characterized in that theprocessing unit or target sensor is provided with correction means forcorrecting the measurement data supplied by the target sensor with theaid of measurement data supplied by the distortion sensor.

In this embodiment, the target sensor accuracy is significantlyenhanced.

A further advantageous embodiment in which the ship is further providedwith a directional apparatus and control means for generating controlsignals for the directional apparatus is characterized in that thecontrol means or the directional apparatus is provided with correctionmeans for correcting the control signals with the aid of measurementdata supplied by the distortion sensor.

The directional apparatus may comprise an optical tracker, a trackingradar or a gun system. In this embodiment, the aiming accuracy of thedirectional apparatus is significantly enhanced.

The invention additionally relates to a distortion sensor arrangementfor measuring the distortion of a ship, comprising:

a light source for generating a narrow light beam to be connected to afirst part of the ship;

a light sensor to be connected to a second part of the ship, designed todeliver a deflection signal of the light beam in response to incidentlight of the light beam on the light sensor.

The advantage of such an arrangement is its capability to continuouslyproduce an electric signal that is representative of the ship'sdistortion, which signal can be used for any purpose required. Thesensor arrangement's sensitivity can be adjusted as considered fit byvarying the distance between the light source and the light sensor.Besides, the measurement is to a large extent temperature-insensitive.

In an advantageous embodiment the light source comprises a laser sourceand the light sensor comprises a CCD array. By means of a laser source,a narrow light beam can simply be generated. The CCD array is designedto register a distortion in two dimensions.

The invention furthermore relates to a system for measuring shipdistortions. The system includes a plurality of distortion sensorarrangements including a light source and a light sensor.

The light source generates a narrow light beam and is connected to afirst part of the ship. The light sensor is connected to a second partof the ship, and delivers a deflection signal in response to lightincident on it.

The system also has a calculation device for calculating the ship'storsional distortion angles and bending distortion angles.

Thus, a system is obtained that is capable of measuring the ship'storsional distortion angles about the pitch axis, and the ship's bendingdistortion angles about the transverse and yaw axes.

A ship incorporating such an arrangement has the advantage that thedistortion can be accurately measured and that the resultingmeasurements can be used for any purpose required.

An advantageous embodiment of such a ship is characterized in that thelight sensor pertaining to one or to all distortion sensor arrangementsis attached to a first frame of the ship with the light source, directedat the light sensor, attached to a second frame of the ship.

In this way, the severest distortion will always be registered, since itoccurs between the comparatively rigid frames. Thus, a high degree ofaccuracy is achieved.

BRIEF DESCRIPTION OF THE FIGURES

The ship and the sensor arrangement according to the invention will nowbe explained with reference to the accompanying drawings, of which:

FIG. 1 is a schematic representation of relevant ship distortions;

FIG. 2 schematically represents a sensor arrangement according to theinvention attached to the ship's frames;

FIG. 3 represents a ship incorporating a plurality of sensorarrangements, a plurality of directional apparatus and a controlcomputer for the directional apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically represents which distortions of a ship 1 arerelevant within the scope of the invention. To this end, the ship isshown in side view A, top view B and perspective C. Side view A and topview C show a longitudinal axis 2 of the ship 1. As known, the ship alsocomprises a pitch axis and yaw axis, not shown. The influence of wateracting on the ship's hull distorts the ship's longitudinal axis 2, asindicated in an exaggerated way by curved lines 3 a, 3 b, 3 c and 3 d,because of the hull bending around the pitch axis and the yaw axis.Likewise, the ship twists around longitudinal axis 2 as indicated bymeans of arrows 4 a and 4 b.

FIGS. 2A and 2B show how two sensor arrangements 5 a and 5 b accordingto the invention can be attached to the ship's frames for the purpose ofmeasuring ship distortions. A section of the ship between two frames isschematically represented as a wire model of a box-shaped body 6, in afirst, normal condition and in a second condition with the ship twistedaround a pitch axis. The two sensor arrangements are mountedsymmetrically in relation to the ship's symmetry plane. A sensorarrangement comprises a laser 7 and a CCD array 9, possiblyincorporating a system of lenses (not shown) for focusing the laser beamonto the CCD-array. The laser is connected to a first frame 9, the CCDarray is connected to a second frame 10. In normal condition, the laserbeam is focused on a central point on the CCD array, creating a laserspot 11. Bending distortion causes the laser spot on the CCD array toshift to point 12 dependent on bending angle 13. The bending distortionaround the yaw axis can be determined analogously.

FIG. 2B represents the same ship's section as shown in FIG. 2A, in thiscase subjected to a torsion 14 around the longitudinal axis. This causesthe laser spots produced by the two sensor arrangements to shiftantisymmetrically in relation to one another. This makes it possible toindependently determine, on the basis of the locations of the laserspots on the CCD array, the degree of torsional distortion around thelongitudinal axis and the degree of bending distortion around the pitchaxis, by performing calculations, by addition or subtraction, on thebasis of measured values produced by the CCD arrays.

FIG. 3 is a schematic representation of a plurality of frames to which aplurality of sensor arrangements are attached to enable an accuratedetermination of the ship's distortion. As the ship is subject tovarious levels of distortion, it is advantageous to arrange for aplurality of sensor arrangements.

The ship is further provided with two directional apparatus, the firstof which incorporates a tracking radar 15 and the second a gun system16. The ship also comprises a position reference unit 17, implemented asa centrally situated gyro system for determining the ship's roll, pitchand heading with respect to a north-horizontal coordinate system. Largenaval ships are usually fitted with two gyro systems, one in the forepart and one in the stern part. A fire control computer 18 determinescontrol signals for the gun system on the basis of data of the trackingradar and the gyro system. The tracking radar is engaged in tracking atarget not shown in the figure, e.g. a missile. The target range anddirection relative to a sensor coordinate system connected to thetracking radar are measured by means of the tracking radar. Theresulting values are subsequently converted to coordinates with respectto a centrally situated own-ship coordinate system. In this respect, thedistance between the sensor coordinate system and the origin of theown-ship coordinate system as well as the alignment angles of the sensorcoordinate system, determined in a prior alignment procedure, inrelation to the own-ship coordinate system, are factors that are takeninto account.

According to the invention, account is however also taken of static anddynamic angular displacements of the sensor coordinate system withrespect to the own-ship coordinate system as a result of the ship'sliability to torsional and bending distortions. To that end themeasurements made by the CCD arrays 8 are supplied to the fire controlcomputer 18 which converts the displacements of the laser spots on theCCD array to these angular displacements. The fire control computersubsequently corrects these target measurements which can of course alsobe corrected in the tracking radar. In case of corrections in thetracking radar, the CCD-array measurements are supplied to a calculationunit incorporated in the radar system. Large naval ships then no longerneed to be provided with two gyro systems, one in the fore part and onein the stern part. A single gyro system, centrally situated, will then,in combination with the angular distortion sensors, be sufficient.

The control signals for the gun system 16 can be corrected analogously.The gun system is thereto connected to a gun coordinate system whoseangular displacements in relation to the own-ship coordinate system aredetermined on the basis of measurements performed by the sensorarrangement.

In order to measure distortion on any given place in the ship on thebasis of a limited number of angular sensor arrangements, aninterpolation may be performed among the various sensor arrangementsconcerning the measured angular distortions.

What is claimed is:
 1. A system for measuring ship distortions that canbe expressed in terms of torsional distortion angles and bendingdistortion angles, the system comprising: a) a first distortion sensorthat continuously measures first torsional distortion and first bendingdistortion, the first distortion sensor including: 1) a first lightsource, connected to a first part of the ship, that generates a firstnarrow light beam; and 2) a first light sensor, connected to a secondpart of the ship, that provides a first deflection signal in response tolight of the first light beam that is incident on the first lightsensor; b) a second distortion sensor that continuously measures secondtorsional distortion and second bending distortion, the seconddistortion sensor including: 1) a second light source, connected to athird part of the ship, that generates a second narrow light beam; and2) a second light sensor, connected to a fourth part of the ship, thatprovides a second deflection signal in response to light of the secondlight beam that is incident on the second light sensor; and c) acalculation device configured to calculate the ship's torsionaldistortion angles and bending distortion angles based on the first andsecond deflections signals.
 2. The system of claim 1, wherein: the lightsource includes a laser source; and the light sensor includes a chargecoupled device (CCD) array.
 3. A ship provided with the system of claim2.
 4. The ship of claim 3, wherein: a particular light sensor isattached to a first frame of the ship; and a particular light sourcethat is directed at the particular light sensor is attached to a secondframe of the ship.
 5. The ship of claim 4, wherein the distortion sensorprovides distortion measurement data; and the ship further comprises: atleast one target sensor that supplies target sensor measurement data; acorrection device configured to correct the target sensor measurementdata in accordance with the distortion measurement data supplied by thedistortion sensor; and a processing unit that processes measurement dataas corrected by the distortion measurement data.
 6. The ship of claim 5,further comprising: a directional apparatus; a control device thatprovides control signals for the directional apparatus; and a correctiondevice configured to correct the control signals.
 7. A ship providedwith the system of claim
 1. 8. The ship of claim 7, wherein: aparticular light sensor is attached to a first frame of the ship; and aparticular light source that is directed at the particular light sensoris attached to a second frame of the ship.
 9. The ship of claim 8,wherein the distortion sensor provides distortion measurement data; andthe ship further comprises: at least one target sensor that suppliestarget sensor measurement data; a correction device configured tocorrect the target sensor measurement data in accordance with thedistortion measurement data supplied by the distortion sensor; and aprocessing unit that processes measurement data as corrected by thedistortion measurement data.
 10. The ship of claim 9, furthercomprising: a directional apparatus; a control device that providescontrol signals for the directional apparatus; and a correction deviceconfigured to correct the control signals.